<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>两列布局解决方案1 - float+margin</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }
    /* float  浮动层叠顺序  >  块级*/
    #left{float:left;width:200px;height:400px;background-color: green;}
    #right{height:600px;background-color: blue;margin-left:200px}
    #inner{
      width: 300px;
      height:300px;
      background-color: gray;
      clear: both;
    }
  </style>
</head>

<body>
  <!-- 定宽 -->
  <div id="left"></div>
  <!-- 自适应容器 -->
  <div id="right">
    <div id="inner"></div>
  </div>
</body>

</html>